10 million cells were harvested, crosslinked with 1% formaldehyde, sonicated, and then subjected to chromatin immunoprecipitation with anti-Blimp-1 antibody. 300-500 bp DNA fragments were obtained after reverse-crosslinking. To generate libraries, DNA fragments were ligated to Illumina’s adapters according to Illumina’s instructions. Briefly, DNA fragments were end-repaired using an END-IT DNA REPAIR KIT#ER0720 Epicentre. The blunt, phosphorylated DNAs were treated with Klenow fragment (Exo-minus, NEB M0212M 50U/ul) and dATP to generate A base overhang. These fragments were ligated with Illumina adapters using a FAST LINK KIT #LK11025 Epicentre. After adapter ligation, DNAs were PCR-amplified with Illumina primers (Primer1.1 and Primer2.1) for 17 cycles and library fragments of 300-500 bp were extracted from an agarose gel.